System requirements for consumer electronics such as cell phones and laptop computers have resulted in the implementation of integrated circuit packages incorporating several semiconductor dies or “chips”. Such multi-chip packages may be realized by connecting multiple semiconductor dies on a single package substrate incorporating interconnects. In this approach, the semiconductor dies are distributed over the surface of the package or stacked on top of each other.
Alternatively, the Package-in-Package (PiP) approach for packaging multi-chip modules involves first mounting a semiconductor die on a package substrate with interconnects, forming an Internal Stacking Module (ISM). This package module can be tested individually prior to assembly into a multi-chip package. Thus the PiP approach provides a means of pre-testing package sub-assemblies (i.e., internal stacking modules), enabling the assembly of complex multi-chip packages using “known good packages.” This modular approach for assembling multi-chip packages reduces overall yield loss.
One important reason for PiP yield loss is warping of internal stacking modules during the PiP assembly process. Cooling and heating cycles encountered in the package fabrication process can induce bending of internal stacking modules due to package asymmetries (both geometry and materials asymmetries). In addition, bending of package substrates used for the ISMs can induce stress concentrations at the corners of the semiconductor die, inducing chip failures. Moreover, a third reason for yield loss is inter-ISM interconnect failures due induced by stress created by temperature cycles encountered in the fabrication process for the package.
Thus, a need still remains for a system for a package-in-package system that can tolerate thermal cycles used for the fabrication process with minimal yield loss. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.